Engagement of mental effort in response to mental fatigue: A psychophysiological analysis 2024 Lorcery et al

Highlights

• A conservative strategy favoring accuracy was adopted during a cognitive task that induced mental fatigue
  
  
• Mental fatigue during a cognitive task leads to a decrease in sympathetic activity with increasing time-on task
  
  
• Mental fatigue induced by a 30-min effortful cognitive task impairs the performance in a subsequent endurance physical task
  

Abstract (max 250 words):

Acute mental fatigue, characterized by a transient decline in cognitive efficiency during or following prolonged cognitive tasks, can be managed through adaptive effort deployment. In response to mental fatigue, individuals can employ two main behavioral patterns: engaging a compensatory effort to limit performance decrements, or disengaging effort, leading to performance deterioration. This study investigated the behavioral pattern used by participants in mental fatigue conditions.

Fifty participants underwent a sequential-tasks protocol with counterbalanced sessions who took place in two separate sessions: a 30-min incongruent Stroop task (fatiguing session) or a 30-min documentary viewing task (control session), followed by a time-to-exhaustion (TTE) handgrip task at 13% of maximal voluntary contraction. Psychophysiological measures included the preejection period, heart rate variability, blood pressure, and respiration. Behavioral results showed deteriorated TTE handgrip performance after the Stroop task compared to after the documentary viewing task. During the Stroop task participants were more conservative and prioritized accuracy over speed. Self-reported fatigue was greater after the Stroop task. Psychophysiological data revealed a gradual decrease in sympathetic activity over time in both tasks, with the Stroop task showing a more pronounced decrease.

Taken together, these findings suggest a disengagement of effort for a large proportion of participants (49%) that could be partly attributed to a habituation to the demands of the Stroop task. This study illustrates the interplay of behavioral patterns of effort investment in the context of mental fatigue and underscores the role of disengagement as a dominant response to this phenomenon among healthy participants.

Paywall, https://www.sciencedirect.com/science/article/abs/pii/S1469029224000712

 

Well this is a sinister and poor attempt at ‘replicating’ Walitts dodgy effort preference using stroop test before hand grip then claiming the format tests something related to effort and habituation instead of exhausting ill people then calling a spade a spade

what the heck do these people think they’ve added in that makes it different from getting someone to exhaust themselves then saying they did less well on the hand grip than those who hadn’t been exhausted first?

this new extremist type manifesto style non science propaganda being allowed to mask in journals as something else taking off is frankly terrifying - what have they become?

 

Their main theory is that people who get tired choose to either further exhaust themselves doing the task properly, or choose to save their energy/effort by Harry half-jobbing. Although, just like Walitt, they don't seemed to have entertained the idea that maybe those who'd been exhausted before just did less well on the next task vs those who hadn't because they were 'impaired' by the exhaustion?

They've measured 'sympathetic activity' (I don't know precisely what they measured within this because I can't read the full paper but it's heart rate type stuff) as some proxy to claim something in I'm assuming the group who 'did the fatiguing task' then doing 'less time' on the hand grip but then suggested:

Doing the stroop requires a lot of concentration but also is exertion trying to differentiate to be saying the colour of the written word whilst blocking out the colour of font . You’d have to be upright and paying attention the whole time and it might give you a headache.

so I can see how being tired from that would affect a grip test which seems to be asking for 13% of maximum over the longest time so need some focus to not over or underdo the grip.

I don’t fully get the control being the documentary other than to hide the aim of the experiment given the exertion of that would be pretty different and you can switch off to it. They’ve even called it just a watching task but it’s like comparing a high involvement computer game to a thirty minute video

so the interpretation being more about ‘effort’ and talk of disengagement and behavioural patterns rather than the concentration equivalent of ‘energy envelope’ if it isn’t an attempt at effort preference claims to replace the idea of mental exhaustion - even if it is in healthy people - it seems an ideology to replace the idea of ‘can’t’ or human beings having points of exhaustion with the idea it’s behavioural?

 

From conclusion —

The refs in the final paragraph are —

Chronic Fatigue in Cancer, Brain Connectivity and Reluctance to Engage in Physical Activity: A Mini-Review (2021, Frontiers in Oncology)

Training Willpower: Reducing Costs and Valuing Effort (2022, Frontiers in Neuroscience)

Réflexions théoriques et méthodologiques autour du concept de fatigue cognitive (2023, Movement & Sport Sciences - Science & Motricité)

Comment lutter contre les effets négatifs de la fatigue mentale : une revue narrative (2023, Movement & Sport Sciences - Science & Motricité)

 

There is the following paper from Bray et al (2012) for example: Cognitive task performance causes impaired maximum force production in human hand flexor muscles - ScienceDirect

That has some interesting references, but I can't see 'in full' (but a bit more than the abstract) which looks at cognitive task inducing central fatigue in muscles on handgrip tasks for example.

And I found the following by Dallaway, Lucas, Ring (2022): Cognitive tasks elicit mental fatigue and impair subsequent physical task endurance: Effects of task duration and type - PMC (nih.gov)

which includes the following in its abstract, which I found interesting from a 'what point induces fatigue' perspective.

And provides reasons like familiarity with the task for the reduction in heart rate.

Compare this to the article above's method:

These authors Dallaway, Lucas, Ring seem to be particularly interested in the area and their 2023 paper: Effects of Stroop task duration on subsequent cognitive and physical performance — University of Birmingham

goes on to look at different time durations and complexities of stroop (congruent and incongruent and number ones), but also then compares models of explanation.

So maybe the 'disengagement' thing wasn't a suggestion of effort preference (although there seem to be some articles linking sympathetic inversely with interest in a task too).

When I looked earlier there did seem to be a bit of a literature associating these types of things (and particularly focusing on the sympathetic / parasympathetic and 'stress') with chronic fatigue or CFS

But then there seems to be an entire literature that is more recent focusing on the 'sympathetic and parasympathetic' as measures in handgrip task-based research and cogntiive tasks where they have focused on stress, and fatigue.

 

Uh, almost like there isn't some separate store of energy for movement, cognition and emotions, rather metabolic energy is metabolic energy and if you deplete reserves other forms of exertion also suffer from poorer performance.

Of course there are other factors limiting this which have no corresponding limits and are independent of energy stores, such as soft tissue, especially using muscles, which has additional limits than just energy, since using them beyond their normal usage tears the fibers. Hence why it makes sense with endurance performance.

This is really is "effort preference" using slightly different words, although as words for this phenomenon, it would be hard to do worse than something suggesting "but I don't wanna, it's too hard, wah wah". It all depends on intent and motivation, and given Wallit's obsession with proving psychosomatic ideology, he chose words to that effect.

 

I think* (this might be influenced by looking at other papers it might be sitting within) they are trying to map 'behaviour' and use 'sympathetic activity' as some sort of indicator as to whether people have chosen to exert less effort (when they got tired) vs 'push through'.

If you look at them using a 30min Stroop then the idea they've exhausted - because most I've seen seem to use maybe 5, 10, 20mins of Stroop - before doing the hand grip. Chances are tbf though even healthy people might have gone right through the wall by then and many of them therefore being on some sort of adrenaline or whatever healthy people need to do in order to keep going. So then suggesting the different % represent 'choice' rather than individual differences in ability and how much something has exhausted them is worrying.

This is where it would also be interesting to see who they recruited from / participants because I can imagine if you have a cohort of students who do every experiment going, but are young so pretty much in the prime age re: all of these 'individual differences' on the systems being pushed to limits here, but also experienced enough to know they can just give up or cruise through for the incentive vs other cohorts. Because sure as heck I'd guess they want to proliferate these to populations but there is an external validity issue if these become some sort of benchmark for 'normal' as if what bored students do informs what eg those with an energy-limiting condition do.

Particularly when their explanations are really just psychological presumption of behavioural explanations as inference being mapped to 'physiological' measures that also relate to all sorts of other things (like someone with ME/CFS being stuck in a chair for 30mins). I remember @Hutan noting that having interviews after EEfRT tasks to ask people what strategy they were using and to actually state their difficulties they experienced on that thread - it seems the case here is that these people didn't do that, and yet their conclusions are pasting in their own 'answers' for the research/measures they didn't actually do?